Synthetic lubricating oil compositions



United States PatentO 2 998 387 SYNTHETIC LUBRICATIbIG OIL COMPOSITIONS David W. Young, Homewood, 111., assignor to Sinclair fiefining Company, New York, N.Y., a corporation of aine No Drawing. Filed May 3, 1957, Ser. No. 656,745

' 8 Claims. (Cl. 252-464) N butyryl-p-amino phenol to increase the stability ofthe lubricant. lnone particular aspect of the invention, my compositions-contain a small amount of abase oil-compatible free .disbasic acid sufficient to increase the elitestiveness of the titanium compound as an extreme pressure agent. When desired, my compositions can also contain various other additives, particularly, phenothiazine as an anti-oxidant.

As set forth inmy application Serial No. 579,140, filed April 19, 1956, now abandoned and its continuation-inpart application Serial No. 647,511, filed March 21, 1957, certain organic titanium-containing compounds which are compatible with synthetic lubricating oils can increase their loadcarrying capacity. These compounds can be prepared by reacting a titanium tetracster and a glycol. Preferred oils are the diester synthetic fluids of lubricating viscosity such as the .di-Z-ethylhexyl sebacate oil sold commercially as Plexol 201. Although the titanium additive imparts the-desired extreme pressure properties to the diester base fluid, the thermal stability characteristics of the lubricantcan be decreased to an undesirable extent apparently due tothe presence of the additive.

In the present invention I have found that this undesirable result can be avoided in the diester base lubricant compositions containing the base oil-compatible organic titanium load carrying agent by incorporating a minor amount of N-butyrylpamino phenol. Accordingly, the lubricating compositions of the present invention contain an amount of the titanium-containing additive which is sufiicient toimpart substantially increased load carrying capacity to the diester base oil and decrease its thermal stability and this amount is usually in the range or about 0.001 to 5 weight percent or more or the total composition. There does not appear to be any necessity for using more than 5 percent. The lubricant also contains sufiicient of the N butyryl-pamino phenol to increase substantially the high temperature thermal stability of the diester oil containing the titanium additive, and this amount usually is in the range of about 0.05 to 3 weight percent. Preferably free, base oil-compatible dibasic acid is present in an amount sulficient to enhance the load carrying capacity of the composition; other additives such as phenothiazine can also be included in the lubricant composition and ordinarily from about 0 to 3 weight percent of phenothiazine will be employed. Generally, when including the phenothiazine it will be at least about-0.05 Weight percent of the composition. The diester base oil oflubricating viscosity is the predominant component of the composition and it comprises substantially the balance considering the various additives included. On a preferred basis the lubricants of the present invention will contain about 0.1 to 2 weight percent When desired,

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of the titanium additive, about 0.1 to 1 weight percent of the N-butyryl-p-amino phenol, and when used about 0.1 to 1 weight percent of phenothiazine and about 0.01 to 0.1 Weight percent of thefree dibasic acid. My various compositions can also contain additional agents such as other anti-oxidants, anti-foaming additives, corrosion inhibitors, v.i. improversother extreme pressure agents, thickeners and other materials added to give desired properties; 1

In the compositions of the present invention the titanium-containing organic material can be used to impart the extreme pressure characteristics to the diester base oils provided for any given use but most significantly these additives exhibit extreme pressure properties in the base oil suflicient to satisfy specifications now promulgated or being considered and of which I am aware. These titanium-containing materials are compatible, i.e. soluble, dispersible or miscible, with the diester base oils. Titanium-containing materials I have found to be useful can be obtained by reacting an organic titanium tetraester with a glycol, and these materials might be derived from other reactants. The resulting products can be monomers or polymers, and, if desired, can be water-washed to approach a water-insensitive for-m. At least certain of these monomer and polymer additives are chelated and have a coordinate valence bond between an oxygen and a titanium atom. Generally, the mere combination of a titanium tetraester and a glycol initiates an exothermic reaction, although if desired heating can be employed. The reaction may proceed only to the monomer stage or continue to a polymer product directly. If a monomer or partially polymerized product be first obtained it can be further polymerized. In any event, I can employ the various products afforded which range from viscous liquids to solids and are compatible in my diester base oils.

Among the titanium esters which I can employ for reaction with the glycol are 'alkyl titanates such as methyl, ethyl, propyl, butyl, 2-ethylhexyl, dodecyl, cyclohexyl and ethoxyethyl tetraesters; aryl tetraesters such as phenyl and beta-naphthyl tetratit-anates; aralkyl esters such as benzyl tetratitanate, mixed esters including diethyl diphenyltetratitanates, mixtures of these materials and their condensed or polymeric organic titanates. The various esters can be substituted in the hydrocarbon ester group although the unsubstituted esters are preferred. The esters prepared from monhydroxy alcohols are used most advantageously. Ordinarily, the separate organic radicals of the titanium tetraester will contain up to about 12 to 18 carbon atoms but may contain more if desired.

Although the additive agents in my lubricant compositions are not limited thereto, among the preferred agents are the products obtained through the reaction of the titanium tetraester with a glycol of the 1,3-diol type, see US. Patent No. 2,643,262 hereby incorporated by reference. As set forth in the patent, these glycols are 2,3 di0rgan0 hydrocarbon substituted materials which have the formula The diorgano radicals, that is the R and R of the glycol forula, can be alkyl, aryl or mixed, and if desired be substituted as with halogen, for instance chlorine. However, R and R should be substantially nonreactive under the reaction and operating conditions employed. Generally, these glycols contain from about 5 to 12 carbon atoms, for instance an octylene glycol; however, if desired they could contain a greater number. Among the specific glycols which can be employed are 2-ethyl-1,3- hexanediol, 2-propyl-l,3-heptanediol, 2-methyl-l,3-pen tanediol, 2-butyl-1,3-butanediol, 2,4 liphenyl-l,3-butanediol, and 2,4-dimesityl-1,3-butanediol.

In addition to these glycols I can employ others and generally the glycols will contain from 2 to about 20 or 24 carbon atoms or more. Also, as indicated above, the glycols may be substituted or unsubstituted as with halogen or another hydroxy radical. Others of the glycols which I can use are ethylene glycol, 2,3-butanediol and ether polyalkylene glycols, for instance where the alkylene radical contains 2 to 4 carbon atoms such as diethylene glycol and dipropylene glycol.

I am not certain of the various structures of the titanium additive agents prepared from titanium tetraesters and glycols but they can be monomeric or polymeric in form. The configuration of these products has been considered in US. Patent 2,643,262, in J.A.C.S., vol. 76, pages 2533-2536, and in my above-identified patent applications, and I hereby incorporate the portions of those applications which are pertinent to the possible structures obtained. As noted in this patent, its various products are said to be characterized by having the structure where R and R are as identified above. It is preferred to employ in the compositions of the present invention the titanium ester-glycol reaction products which are relatively insensitive to water and these are obtained either by reacting the titanium tetraester with sutficient glycol to occupy all of the titanium valences, or by using a lesser amount of glycol and water washing the product so that any ester group of the original titanium tetnaester remaining is replaced by a hydroxyl radical.

In spite of the uncertainties of the structures of the additive agents prepared from the titanium tetraesters and glycols, the base oil-compatible titanium compounds can be produced through reaction, with or without heating, of about /2 to 4 moles of glycol with each mole of titanium tetraester, preferably about 2 to 4 moles of glycol per mole of titanium tetraester. The first product obtained in the reaction can be employed in my invention or polymerized through heating or through. water addition and heating with there being no particular critical limitation on either, except of course the temperature should not be so high as to decompose the desired reaction products. Ordinarily, the polymerization temperature will be above about 25 C. and preferably at least about 40 C. When employing heat to obtain a polymer in the absence of water and from a monomer dissolved in a solvent, it may be desirable to use a vacuum, say about 5 to 10 millimeters of mercury and a temperature of about 130 to 170 C. to remove the solvent while forming the polymer. Other conditions of temperature and pressure could be employed.- Among the suitable inert solvents which can be employed are cyclohexane, n-butane, benzene, etc. If water be present during polymerization I usually employ at least 1 part per part of titanium tetraester with 2 to 20 parts of water being used most advantageously. At the end of the reaction, alcohol and water can be boiled oif or otherwise removed. The length of time the heating is conducted can be varied widely and is'not critical, and apparently during polymerization non-chelated groups of the titanum reactant are hydrolyzed from the molecule. Several of my titanium extreme pressure agents prepared from the titanium tetraester and a glycol have been made available by E. I. duPont de Nemours & Company.

4 For instance, they otter for sale materials of the following table:

from liquid to solid as long as they are compatible with the base oil. Frequently when the titanium additive is in polymeric form the molecular weight will be about from 800 to 3000 and preferably from about 1000 to 1800 but the molecular weight may even be as high as 5000'to 15,000 or 20,000 or more. Advantageously, I employ the low molecular weight polymers as they do not tend to thicken the base lubricating oil. The low molecular weight OGT-derived polymer additives frequently have viscosities at F. rangingfrom about 0.575 to 0.85 centistokes on the basis of 1 gram in 40 grams of toluene. My OGT monomers and their polymers made by heating in the presence of water can be blended with the diester base oil at room temperature but slight heating is preferred when blending these polymers. Such polymers made by heating the monomers in the absence of water seem more diflicult to combine, and temperatures of at least about F. are generally employed during the blending of these materials.

My compositions contain sufiicient of the titanium additive agent to increase materially the load carrying capacity of the base oil. Generally, the final lube composition will contain from about 0.001 to 5 weight percent of the additive agent and I prefer about 0.1 to 2%. More than 5% could be used but there does not appear to be any necessity for thus. The actual amount of agent employed may be dependent upon the degree of improvement desired and upon factors such as the character of the base 'oil and the other materials which may be added to or be present in the lubricant composition.

It has been found that variations in the amount of additive or titanium supplied to diester synthetic base lubricants can significantly influence the degree of improvement in their load carrying properties. Thus, the addition to several essentially dibasic acid-free diester synthetic oils of 0.2% of my titanium agent, in the form of a 20% OGT-41 polymer concentrate in Plexol 201 (Plexol 201 contains about 0.02% of free sebacic acid), produced compositions which although improved in extreme pressure properties did not satisfactorily carry 3000 lbs. in the Ryder test machine. However, when 1% of OGT-41 polymer was added to an essentially dibasic acid-free di-Z-ethylhexyl sebacate base composition, the oil had a load carrying ability of about 5000 lbs. in the test, see my application Serial No. 647,511.

p The degree of improvement in the load carrying properties of diester synthetic oils afforded by incorporation of my titanium additives can be materially enhanced by providing in the composition a small but effective amount of a free, base oil-compatible dibas'ic acid. Generally, the compatible acids I use have molecular weights of up to about 600 which includes for instance monomer and dimer acids. Thus,'I can employ at least about 0.005 weight percent of a dibasic a'cid,'preferably having from 2 to about 12 or 20 carbon atoms such as those named herein, in these lube compositions and obtain improved 8 extreme pressure properties, particularly when the amount of titanium additive is such that the .compositioncontains up to about 0.1 weight percent of titanium, preferably upto about 0.05 weight percent of titanium. Of course, the dibasic acid could be present when the lubricant contains more than about 0.1 weight percent of titanium should it be considered desirable. In my preferred embodiment the free dibasic acid is about 0.01 to 0.1 weight percent of the composition, and generally there seems to be little if any benefit to be derived from using more than about 1% of the acid when it is added primarily to enhance the effectiveness of the titanium additive. -Although the dibasic acids have been found to be useful along with my titanium additives the same result has not been obtained by incorporation of the monobasic acid, decanoic acid, or the half ester prepared from 2-ethylhexanol and sebacic acid. The use of the small amount of dibasic acid to enhance the actionof the titanium additives towards imparting improved load carrying characteristics to the synthetic base oils is particularly desirable where the amount of improvement wanted cannot be obtained by employing the titanium additive alone without using an amount of the latter which contributes to the final lubricant composition another characteristic which is deleterious in a given situation. For instance, there is some indication that when a Plexol 201 base lubricant containing phenothiazine and a silicon anti-foaming agent has incorporated in it more thanabout 0.05 weight percent of titanium in the form of an OGT-41 polymer the composition exhibits lead and magnesium corrosion properties to an extent which at this time seems undesirable for high temperature jet engine use.

The base oils of my compositions are the diester synthetic oils of lubricating viscosity which consist essentially of carbon, hydrogen and oxygen. Various of these lubricating materials have been described in the literature and generally their viscosity ranges from the light to heavy oils, e.g. about 50 SUS at 100 F. to 250 SUS at 210 F., and preferably 30 to 150 SUS at 210 F. The base lubricating oil can, if desired, be treated with gamma-rays. The diester base oils are made from alcohols and polycarboxylic acids. Among the acids employed are those of 2 to 12 carbon atoms particularly the dicarboxylic aliphatic acids such as adipic, azelaic, suberic, alkenyl succinic, sebacic, etc. The alcohols employed usually contain less than about 20 carbon atoms and are generally aliphatic such as the butyl, hexyl, 2- ethylhexyl, and dodecyl alcohols. The alcohols can also be poly-functional materials such as glycols and included among the glycols are the ether glycols. Among my useful diester base oils are those disclosed in US. Patents Nos. 2,499,983; 2,499,984; 2,575,195; 2,575,196; 2,703,- 811; 2,705,724 and 2,723,286.

As I have mentioned my diester basic oils consists essentially of carbon, hydrogen and oxygen, that is the essential molecular chemical structure is formed by these elements. However, these oils may be substituted with other elements such as the halogens, chlorine and fluorine, for instance the fluorinated esters of dibasic acids. Among the specific synthetic oils falling within the above classes are di-(Z-ethylhexyl) sebacate, di-(2-ethylhexyl) phthalate, di-(l,3-methylbutyl) adipate, di-(2-ethylbutyl) adipate, di-(l-ethylpropyl) adipate, bis (lH,lH,7H-dodecafluoroheptyl) -3-methyl glutarate, di-(cyclohexyl) adipate, di-(undecyl) sebacate, di-benzyl sebacate and di-(2-ethylhexyl) azelate.

In preparing the OGT polymer additives, I prefer to take 1 part by weight of OGT-41 and 1 to 6 parts by weight of water and heat the mixture to at least about 60 F. while agitating. The temperature is held for about 15 to 60 minutes and agitation is then stopped. A white, sticky, insoluble, elastic polymer settles while octylene glycol and butanol solvent form an upper layer. The top layer and the Water layer are decanted and the polymer is Water Washed and blended with the base oil, for in PREPARATION NO. 1

164 pounds of OGT-41 were weighed into a stainless steel Pfaudler kettle. While stirring vigorous-1y, 210 pounds of tap water were added. The stirred mixture of water and precipitated polymer was heated to F. over a twenty-minute period. When the mixture reached 170 F., the agitation was stopped, and the mixture was allowed to settle 1 hour. The upper organic layer and water were siphoned off the wet polymeric white solid. A second charge of tap water, 210 pounds, was added to the kettle, while agitating vigorously, and the mixture was heated to 170 F. The agitation was stopped, and the mixture was allowed to settle two hours. The bulk of the water was siphoned off the polymer; the last part of the water was drained through the Wet granular polymer to the bottom valve on the kettle and discarded. 147 pounds of Plexol 201 were then charged to the stirred kettle, and the contents heated to F. At about 180 F., the polymer was dissolved. The agitation was stopped, and the solution settled for 30 minutes. The lower Water layer was drawn off, and discarded. At this point the organic layer was almost clear, except for a slight water haze. The organic layer was dehydrated by heating to 250 F. and cooled to 80 F. Product yield was pounds of clear yellow liquid, having the following analysis:

Kinematic Viscosity at 100 F., cs 1647 at 210 F., cs 3.691 Titanium, wt. percent 3.20 Acid Number (ASTM-D974) 3.10 Approximate Additive Concentration, Wt. percent- 20.0

PREPARATION NO. 2

1 part by volume of OGT-41 was added to a stainless steel beaker and heated with agitation to 200 F. After this temperature was reached, 2 parts by volume of water were slowly added and agitation continued for about 30 minutes. The liquid phase was decanted and the white polymer solids were washed with an equal part of water. The water was decanted, the solids were filtered and then air dried at 25 C. The resulting white polymer had a molecular weight of 1370 and an ash of 28.39 weight percent. An additive concentrate of this polymer was prepared by dissolving it in two parts by weight of Plexol 201 per part of polymer.

The following specific examples will serve to illustrate the present invention but they are not to be considered limiting.

Several synthetic lubricant compositions which were prepared using Plexol 201 as the base lubricant will be used to illustrate the advantages of my present invention. In the following table are given three compositions, the first of which is the base oil Plexol 201. The second composition includes this base lubricant and 0.5 weight percent of the OGT-41 polymer-Plexol 201 blend made in the presence of water essentially as set forth above in Preparation No. 2. The third composition is the same as the second except that the former includes 0.5 weight percent of N-butyryl-pamino phenol in addition to the OGT-41 polymer.

The thermal stability of these lubricants is tested by a heat-soak method. In this test a three-necked flask is employed and in its center neck is placed a sample tube for the lubricant. This tube extends into 1 liter of cetane held in the flask. The sample tube is fitted with a Friederichs condenser having a line of application of a vacuum or introduction of nitrogen. The sample tube has a line for collecting materials evolved from the lubricant and this line leads to a receiving flask. One side neck of the three-necked flask is stoppered and the other side neck is fitted with an air condenser leading to a nitrogen inlet.

In the test, the sample tube is weighed to the nearest milligram and then 20 to 30 grams of the lubricant undergoing test are introduced. The tube and its contents are again weighed to the nearest milligram. The sample tube is fitted into the three-necked flask containing the cetane and the flask is swept with prepurified nitrogen for 5 minutes to remove air. A vigorous nitrogen flow is then supplied to the Friederichs condenser after which this system is evacuated to 1 to 2 millimeters of mercury. This alternate nitrogen flow-vacuum application cycle is repeated twice and thereupon a slight flow of nitrogen is passed into the Friederichs condenser to the end of the test. The cetane bath in the three-necked flask is then brought to a boil as quickly as possible and usually it takes less than /2 hour to reach the boiling point of 544 to 546 F. After the boiling point is reached the heat is cut back to maintain steady reflux for hours. At the end of this time the heat supply is cut oil and the test apparatus sits to cool to room temperature. The sample tube and its contents are then weighed to the nearest milligram and the weight loss is recorded. Other tests can be made on the sample lubricant, such as acid number, viscosity and saponification number changes.

1 Plexol 201 is a di-2ethylhexyl sebacate having a kinematic viscosity at 100 F. of about 12.7 centistokes a viscosity index of 154, a pour point of below 80 F. and an acid num er of 0.12.

From these data it is seen that the base lubricant Plexol 201 has good thermal stability; however, its load carrying capacity is about 2100 lbs. in the Ryder Gear Test Machine which is below the 3000 lb. minimum required in the MIL-L-25336 (ASG) specifications. When in composition No. 2 of Table I the OGT-41 polymer is added to provide load carrying capacity to the base fluid in excess of the 3000 lb. minimum specification, the thermal stability of the lubricant is deleteriously afiected. Thus, the weight loss goes from 0.711% to 2.08% and the acid number increase rises from 3.74 to 11.02. The saponification number increase of lubricant No. 2 is 8.7 as compared with 0.5 for the base lubricant No. 1.

Byreference to the data gathered in testing luubricant No. 3, it is seen that the addition of the N-butyryl-pamino phenol to lubricant No. 2, brings the weight loss down to below that experienced with the base fluid and at the same time the acid number increase is only 5.82 while the saponification increase is 1.9. All viscosity measurements made at 100 and 210 8 MILL-specification. In elfect, the addition of the N-butyryl-p-amiuo phenol to the titanium-containing diester synthetic lubricant provides a composition of satisfactory load carrying capacity and at the same time the thermal stability of the product is superior to that of the lubricant containing only the base fluid and the titanium additive.

Tests have also shown that the N-butyryl-p amino phenol increases the thermal stability of the diester base oil containing phenothiazine as well as the titanium-containing extreme pressure additive. The data of Table H illustrate this point:

Table II Lubricant N 0. Composition, Wt. Percent Plexol 201 Balance Balance Balance DOF 200-60,000 1 0. 0005 0.0005 0.0005 Phenothiazine 0. 5 0. 5 0. 5 OGT-41 Polymer-Plexol 201 blend of To give(.03% of titanium in Preparation No. 1. 'omposltion N-butyryl-p-amino phenol. 0.25 0.5 Test Conditions:

Length, hours 10 10 Temperature, F 544-546 544-546 544-546 Test Results:

Weight Loss, Percent. 1. 0. 201 0.685

I Viscosity at 210 F., cs.-- 3. 320 3.350 3.386

Percent Vis. Changeat 210 3.76 0.089 0.148 at F.-..... 12.8 1. 50 0.690 Percent Decomposition 2. 89 1. 76 2. 22

1 DCF-20060,000 is a methyl silicone polymer having a viscosity of 60,000 cs. at 25 C. and is an anti-foaming agent.

This application is a continuation-in-part of my application Serial No. 633,520, filed January 11, 1957, now abandoned.

I claim:

1. A lubricating oil composition consisting essentially of a diester oil base of lubricating viscosity prepared from dicarboxylic acids containing from about 2 to 12 carbon atoms and alcohols containing less than about 20 carbon atoms and having incorporated therein about 0.001 to 5 weight percent of a base oil-compatible organic titanium-containing material formed by the reaction of a titanium tetraester with a glycol containing from 2 to about 24 carbon atoms, said titanium tetraester and glycol reacting in the ratio of about 2 to 4 moles of glycol to each mole of titanium tetraester, said titanium-containing material being present in an amount suflicient to increase the load carrying capacity of the base oil and decrease its thermal stability, and N-butyryl-p-amino phenol in an amount to improve the thermal stability of the base oil including the titanium-containing material.

2. The lubricating composition of claim 1 in which there is present an amount of a base oil-compatible dibasic acid sufficient to provide increased load carrying capacity to the composition.

3. The lubricating composition of claim 2 in which the titanium-containing material is present in an amount from about 0.1 to 2 weight percent and N-butyryl-pamino phenol is present in an amount from about 0.1 to 1 weight percent.

4. The lubricating composition of claim 2 which contains about 0.05 to 3 weight percent of phenothiazine.

5. The lubricating composition of claim 2 in which the titanium-containing additive is a base oil-compatible polymer of the titanium tetraester and glycol.

6. The lubricating composition of claim 2 in which the base oil is di-2-ethylhexyl sebacate.

7. The lubricating composition of claim 2 in which is included about 0.05 to 3 weight percent of phenothiazine in which the base oil is di-Z-ethylhexyl sebacate in which the titanium-containing material is a polymer of the titanium tetraester and the glycol and in which the dibasic acid is sebacic acid and is about 0.01 to 0.1 weight F. satisfy the noted 15 percent of the composition.

8. A lubricating oil composition consisting essentially of di-Z-ethylhexyl sebacate base oil having incorporated therein about 0.1 to 2 weight percent of a base oil-compatible polymeric titanium-containing material of the reaction product of a titanium tetraester with a glycol containing from 2 to about 24 carbon atoms, said titanium tetraester and glycol reacting in the ratio of about 2 to 4 moles of glycol to each mole of titanium tetraester, said titanium-containing material being present in an amount suflicient to increase the load carrying capacity of the base oil and decrease its thermal stability, about 0.1 to 1 weight percent of N-butyryl-p-amino phenol to improve the thermal stability of the base oil including the titanium-containing material, about 0.1 to 1 weight percent of sebacic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,190,648 Cantrell Feb. 20, 1940 2,368,604 White Jan. 30, 1945 2,375,007 Larsen May 1, 1945 2,625,557 Cottle et a1. Jan. 13, 1953 2,788,326 Bondi et lal. Apr. 9, 1957 2,795,553 Lowe June 11, 1957 10 2,824,838 Young et al. Feb. 25, 1958 OTHER REFERENCES Cohen et al.: Aliphatic Esters, Industrial and Engineering Chemistry, vol. 45, August 1953, pp. 1766-1775. 

1. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A DIESTER OIL BASE OF LUBRICATING VISCOSITY PREPARED FROM DICARBOXYLIC ACIDS CONTAINING FROM ABOUT 2 TO 12 CARBON ATOMS AND ALCOHOLS CONTAINING LESS THAN ABOUT 20 CARBON ATOMS AND HAVING INCORPORATED THEREIN ABOUT 0.001 TO 5 WEIGHT PERCENT OF A BASE OIL-COMPATIBLE ORGANIC TITANIUM-CONTAINING MATERIAL FORMED BY THE REACTION OF A TITANIUM TETRAESTER WITH A GLYCOL CONTAINING FROM 2 TO ABOUT 24 CARBON ATOMS, SAID TITANIUM TETRAESTER AND GLYCOL REACTING IN THE RATIO OF ABOUT 2 TO 4 MOLES OF GLYCOL TO EACH MOLE OF TITANIUM TETRAESTER, SAID TITANIUM-CONTAINING MATERIAL BEING PRESENT IN AN AMOUNT SUFFICIENT TO INCREASE THE LOAD CARRYING CAPACITY OF THE BASE OIL AND DECREASE ITS THERMAL STABILITY, AND N-BUTYRYL-P-AMINO PHENOL IN AN AMOUNT TO IMPROVE THE THERMAL STABILITY OF THE BASE OIL INCLUDING THE TITANIUM-CONTAINING MATERIAL. 